ActiveRecord::JsonAssociations

Instead of keeping the foreign keys on the children, or in a many-to-many join table, let's keep them in a JSON array on the parent.

require "active_record/json_associations"

ActiveRecord::Schema.define do
  create_table :parents do |t|
    t.json :child_ids, default: []
  end

  create_table :children
end

class Parent < ActiveRecord::Base
  belongs_to_many :children
end

Note: The child_ids column must be a native JSON type. Text columns are not supported.

This will add some familiar has_many-style methods:

parent.children? #=> false

parent.children = [Child.create!, Child.create!, Child.create!]
parent.children #=> [#<Child id: 1>, #<Child id: 2>, #<Child id: 3>]

parent.child_ids = [1,2]
parent.child_ids #=> [1,2]

parent.children? #=> true

And a scope method for finding records associated with an id:

Parent.child_ids_including(2) # => [<Parent child_ids: [1,2,3]>]

Or any of a specified array of ids:

Parent.child_ids_including(any: [2,4,5]) # => [<Parent child_ids: [1,2,3]>]

touch: true can be specified on belongs_to_many to touch the associated records' timestamps when the record is modified.

It also adds an json_foreign_key option to has_many for specifying that the foreign keys are in a json array.

class Child
  has_many :parents, json_foreign_key: true # infers :child_ids, but can be overridden
end

child = Child.create!
parent = Parent.create children: [child]
child.parents == [parent] #=> true

I can't figure out how to support building records off the association, so instead there are the has_one/belongs_to builder methods:

child.build_parent
child.create_parent
child.create_parent!

# also supports optional attributes:

child.build_parent(name: "Momma")

• Ruby 3.2+
• ActiveRecord 7.2+
• Database with JSON column support (MySQL, PostgreSQL, SQLite 3.9+)

1. Fork it ( https://github.com/botandrose/active_record-json_associations/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request